Japanese Patent Application Publication No. 10-303562 (JP 10-303562 A) (Patent Document 1) discloses a technology of a circuit substrate that facilitates wiring and that enables stable power supply. In the case where a semiconductor module of a BGA (ball grid array) type with a multiplicity of connection terminals or the like is mounted on a circuit substrate, it is difficult to complete all wiring in only a wiring layer on a surface layer of the circuit substrate. Therefore, a circuit substrate on which such a semiconductor module is to be mounted generally has a plurality of wiring layers and through holes that connect between the plurality of wiring layers. Such a semiconductor module tends to consume much power, and it is desired that power supply wiring for supplying power should have a large wire width. In the document mentioned above, disconnection of the power supply wiring and a reduction in the area of the power supply wiring are suppressed with the power supply wiring around the through holes removed in order to keep insulation between the through holes for signal transfer and the power supply wiring. Specifically, stable power supply is enabled by securing sufficient width and area of the power supply wiring by avoiding connection of wiring-removed regions of the power supply wiring by arranging the through holes which penetrate the power supply wiring regularly. Since the through holes penetrate the power supply wiring, however, the effective area of the power supply wiring in the region occupied by the power supply wiring is reduced by an amount by which the wiring-removed regions which prevent conduction with the through holes are provided. Thus, there is desired a technique of providing power supply wiring that has a large effective area without being affected by the through holes.